Aperture/shutter system and a stepper motor for use therein

ABSTRACT

An aperture/shutter system defining an optical path comprises a shutter mechanism operable at a first state to selectively block light along the optical path and a second state to allow light along the optical path; and a motor including a stator and an annular rotor. The rotor is rotably supported within the stator by a support that is (i) stationary with respect to the stator and (ii) engages an inner surface of the rotor. The rotor is coupled to the shutter mechanism to move the shutter mechanism between the first state and the second state.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following applications filedconcurrently herewith: "Aperture/Shutter System with A Motor Component"by Jean F. Depatie, et al (Attorney Docket No. 78421/SZS); and "AnImaging Apparatus with A Motor Component" by Jean F. Depatie, et al(Attorney Docket No. 78728/SZS).

FIELD OF THE INVENTION

The present invention relates in general to a motorized aperture and/orshutter system for use in photographic cameras and to small steppermotors suitable for use in such systems.

BACKGROUND OF THE INVENTION

A typical photographic camera includes a lens barrel assembly comprisingat least one barrel supporting one or more lens elements and a shutterassembly. Such a shutter assembly 5 is illustrated in FIG. 1. Theshutter assembly 5 includes a ring 20 and several blades 10a, 10b, 10cthat open by a variable amount to provide the desired aperture for theproper exposure. The shutter assembly is enclosed by the two housingparts 18A and 18B. The movement of the blades is controlled by a piniongear 22 of a stepper motor 24 via use of the ring 20. The motor 24 andthe pinion gear 22 are located external with respect to the shutterassembly. The ring 20 includes a sector gear with a plurality of gearteeth 20b that engages the teeth of the pinion gear 22. Thus, when therotor 24a of the stepper motor 24 rotates, the pinion gear 22 attachedto the stepper motor 24 also rotates, rotating the ring 20. The ring 20includes posts 20a which are coupled to the slots 10a', 10b', 10c' ineach of the blades 10a, 10b, 10c. The rotation of the ring 20 moves theblades, changing the size of the aperture. The blades 10a, 10b, 10c aremoved in a series of steps from the closed position to achieve thedesired aperture size, stay in this position for the desired exposuretime and then reverse into the closed position. This configurationresults in multiple parts, complex assembly and the expense due toprecision alignment of the stepper motor to the shutter assembly, andthe alignment of the gear teeth of the pinion gear to the poles of thestepper motor 24.

In addition, the shutter assembly is a separate part from the lensbarrel assembly. Thus, the shutter assembly and the lens barrel assemblyneed to be precision aligned with respect to one another. This type ofalignment is difficult, expensive and produces an incorrect exposure ifthe alignment is not performed properly. Finally, this configurationresults in a large package size.

U.S. Pat. No. 4,005,448 discloses a programmable shutter and uses astepper motor to control its position. The patent describes constructionof the stepper motor for shutter actuator control and a control circuitfor supplying the pulses to the stepper motor and aperture/shutterdriver control circuit. More specifically, FIG. 4 of this patentillustrates that the motor comprises a stator and rotor with a centralopening and, the shutter comprises three blades also forming an opening.The light passes through the central opening of the rotor and throughthe opening formed by the blades. This figure also shows that a ballbearing is used to maintain the proper positioning between the statorand the rotor. The proper gap between the rotor and stator is criticalto allow for proper operation of the motor assembly. Thus, the stator,the ball bearing and the rotor have to be manufactured to hightolerances and carefully assembled with respect to one another. Inaddition, the rotation of the ball bearing has to overcome itsrotational inertia, which requires power, and reduces the amount oftorque generated by the motor and affects its uniformity. The assemblyof many parts to form a motor in itself increases the motor size andmotor complexity. Furthermore, the patent does not describe alignmentbetween the lens barrels and the shutter assembly. As stated above, theprecision alignment of the stepper motor to the shutter assembly and theprecision alignment of the shutter assembly to the lens barrel assemblyis expensive, and may result in an incorrect exposure if the alignmentis not performed properly. Finally, the stepper motor and the shutterassembly disclosed in the U.S. Pat. No. 4,005,448 form different andseparate parts from the lens barrel assembly. The shutter assembly stillneeds to be aligned to the lens barrel assembly. The alignment of theshutter assembly to the lens barrel has to be accomplished external tothe shutter assembly. The patent does not disclose how this alignment isbeing done. In addition, the disclosed shutter assembly is large.

U.S. Pat. No. 4,596,449 describes a zoom drive mechanism for moving thelens units (also referred to as lens groups) to varying zoom positionsand, therefore, for changing the focal length of the zoom lens systemand for the fine focus adjustment. This zoom drive mechanism utilizes astepper motor comprising a stator and a rotor. The stepper motorelements are mounted to the lens barrels. The rotation of the rotormoves the lens barrels. An improper assembly of the motor to the lensbarrels can result in a wrong focal length and degraded image quality.This patent is silent with respect to the issue of aperture/shuttercontrol.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an aperture/shuttersystem that overcomes the problems exhibited by the prior art. It isalso the object of the present invention to provide an aperture/shuttersystem that is very compact, has a minimum number of mechanical partsand provides a highly uniform torque. It is also an object of thepresent invention to provide an aperture/shutter system which isrotationally symmetric about an optical axis, has a large centralopening, and is easy to assemble.

According to one aspect of the present invention, an aperture/shuttersystem defining an optical path comprises a shutter mechanism operableat a first state to selectively block light along the optical path and asecond state to allow light along the optical path; and a motorincluding a stator and an annular rotor. The rotor is rotably supportedwithin the stator by a support that is (i) stationary with respect tothe stator and (ii) engages an inner surface of the rotor. The rotor iscoupled to the shutter mechanism to move the shutter mechanism betweenthe first state and the second state.

According to another aspect of the present invention, a motor suitablefor use in an aperture/shutter system comprises a stator and an annularrotor arranged inside the stator. The rotor has having an outer surfacefacing said stator and an inner surface and is rotably supported withinthe stator by a support that is stationary with respect to the stator.This support is adjacent to the inner surface of the rotor.

According to one embodiment of the present invention the motor alsoincludes a housing encasing the stator. This housing includes a hubproviding the support for the rotor and a lens seat supporting at leastone lens element.

According to yet another aspect of the present invention an imagingsystem comprises: (i) a plurality of lens elements defining an opticalaxis; (ii) a shutter mechanism including a plurality of shutter blades;and (iii) a motor including a stator and an annular magnetic rotorarranged inside said stator. The rotor is rotably supported within thestator by a support that engages an inner surface of the rotor and isstationary with respect to the stator. The rotor is axially aligned withthe stator along the optical axis. The stator in combination with therotor causes rotation of the shutter blades.

The above, and other objects, advantages and novel features of thepresent invention will become more apparent from the accompanyingdetailed description thereof when considered in conjunction with thefollowing drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art aperture/shutter system.

FIG. 2 is an exploded view of a directly coupled stepper motoraperture/shutter system of the first embodiment of the presentinvention.

FIG. 3 is a perspective view of an integral stepper motor housing and astator assembly.

FIG. 4 is an enlarged view of an integral stepper motor housing andstator assembly.

FIG. 5A is an exploded view of a stepper motor housing, a stator that isbeing assembled into this housing, a rotor, shutter blades, separatorsand a cover.

FIG. 5B is an exploded view of a stepper motor housing, a stator that isbeing assembled into this housing, a rotor, shutter blades, separatorsand a cover that includes a lens set.

FIG. 6 is a perspective view of a stepper motor housing, stator, rotor,shutter and cover assembly.

FIG. 7 is a cross sectional view of the assembly of FIG. 6.

FIG. 8 is a cut-out view of the assembly of FIGS. 6 and 7 but withoutthe rotor.

FIG. 9 is an exploded view of a directly coupled stepper motoraperture/shutter system of another embodiment of the present invention.

FIG. 10 is a perspective view of the stepper motor housing and statorassembly shown in FIG. 9.

FIG. 11 is an exploded view a zoom lens assembly.

DETAILED DESCRIPTION OF THE INVENTION

The present description will be directed in particular to elementsforming part of an apparatus in accordance with the present invention.It is understood that elements not specifically shown or described maytake various forms well known to those skilled in the art.

FIG. 2 shows the aperture/shutter system of the first embodiment of thepresent invention. This aperture/shutter system has a plurality ofblades that serve as a shutter and that form an aperture that limits theamount of light entering into an lens system (not shown) and, thus, theblades also serve as an aperture stop for the lens system. Morespecifically, in this embodiment an aperture/shutter system 100comprises (i) a shutter with a plurality of blades 110, each including aslot 110a, and a hole 110b, (ii) a doughnut like aperture/shutterhousing 112 with an internal central hub 112a and (iii) a stepper motor113 at least partially enclosed by the housing 112. The housing 112 hasat least one and preferably more posts 112b in its rear wall 112c (seeFIG. 3) for engaging the holes 110b of the blades 110 and providing apivot support for the blades 110. The blades 110 move, thereby providinga variable aperture opening. A more detailed description of the blades110 is provided further in the specification. The inner wall 114 of thehousing 112 forms a hollow cylinder for providing access to the lightpropagating along an optical path (through one or more of the lenselements that form the lens system) towards an imaging area 115 on aphotosensitive media such as film 116, or an electronic light sensitivedevice, for example a CCD array (not shown). When one or more lenselements are placed into this hollow cylinder, the length of the lenssystem (along the optical axis) and the diameters of the lens elementsare reduced, because the lens elements are located as close as possibleto the aperture stop (formed by the blades 110). The housing 112 mayalso include hemispherical location pads 114a, a slot 114b and mountingfeatures 112d for a cover 114c. This is illustrated in FIG. 3. Thefunctions of the pads 114a and the slot 114b are described further inthe specification.

Referring to FIG. 4, the stepper motor is a magnetic motor thatcomprises a stator 120 formed with two stator assemblies 120a, 120b. Thetwo stator assemblies 120a, 120b each include a coil 121 of a tightlywound wire and two metal parts 122, 123 surrounding each of the coils121. (FIG. 4) These metal parts 122, 123 include projections formingteeth 124 that interleave with one another at a close proximity to oneanother. The teeth 124 act as magnetic poles of the stator 120. Morespecifically four such interleaved teeth 124 form four poles of thestepper motor 113. The teeth 124 form an inner cylindrical wall 125 ofthe stator (see FIG. 3).

The stator assemblies 120a, 120b of the stepper motor 113 are locatedinside the aperture/shutter housing 112, are partially enclosed by thishousing and, preferably form an integral part of the aperture/shutterhousing 112, for example, by having the plastic aperture/shutter housing112 molded, extruded, or cast around the stator 120. As used herein, theterms "integral" and "integrally" are defined as being made or formed asa single unit, for example, by casting or molding and does not mean thatthe pieces are assembled together after their manufacture. For example,in this embodiment, the aperture/shutter housing 112 is not made as aseparate piece that is later attached to the stator 120.

More specifically, in this embodiment of the present invention the metalparts 122, 123 of the stator assemblies 120a, 120b are assembledtogether and are then encased into the plastic aperture/shutter housing112 by injection molding the aperture/shutter housing 112 around thestator 120. During the injection molding process, locating pinspositioned in the forming apparatus (i.e., a mold) used for injectionmolding hold the two stator assemblies 120a, 120b in a predeterminedlocation, as the plastic aperture/shutter housing 112 is being moldedaround these stator assemblies 120a, 120b. Because the aperture/shutterhousing 112 is molded around the stator assembly and is integralthereto, the stator 120 provides the required rigidity to theaperture/shutter housing and, the plastic walls of the aperture/shutterhousing 112 are made very thin, without compromising the rigidity of theoverall aperture/shutter housing 112. Because of this, theaperture/shutter housing 112 is very compact. More specifically, theaxial length of the aperture/shutter system and the ratio of the outsidediameter d₁ of the aperture/shutter housing 112 to its inner diameter d₂(see FIG. 2) are very small because the stepper motor 113 is integratedinto the aperture/shutter housing 112 and, because the entireaperture/shutter system is symmetrical (with respect to the optical axisdefined by the lens elements centered about this axis). It is preferredthat the outside diameter d₁ be small (for example, about 28 mm and morepreferably 26 mm or less) and that the ratio of an outside diameter ofd₁ to the inner diameter d₂ be 2.5<d₁ /d₂ <3.4. It is most preferablethat this ratio be 2.7<d₁ /d₂ <3.3. For example, in one implementation,the outside diameter d₁ of the housing 112 of this embodiment is 25 mmand its inner diameter d₂ is 8.0 mm. Therefore, the ratio of an outsidediameter of d₁ to the inner diameter is 3.18 and, thus, the annular sizeΔ=d₁ -d₂ of the aperture/shutter system is very small, i.e., Δ=d₁ -d₂=8.5 mm. In another implementation, the outside diameter d₁ of thehousing 112 is 22 mm and the inner diameter d₂ is 8.0 mm. Therefore, theratio of an outside diameter of d₁ to the inner diameter is 2.75 and,thus, the annular size Δ is 7 mm. This small annular size is one of theadvantages of the present invention. Insert molding plastic housing 112around the stator 120 further reduces the overall size of theaperture/shutter system since the components do not need to be molded asdiscreet parts. Since some of the rotor components are eliminated, thisresults in a very compact aperture/shutter system. In addition, becausethe rear wall 112c of the aperture/shutter housing 112 is very thin(about 0.4 mm to about 0.9 mm), the lens elements can be located veryclose to the aperture stop. For manufacturing reasons, it is preferredthat the wall thickness be 0.6 to 0.8 mm. In this embodiment it is about0.7 mm. Although the housing walls are very thin, the rear wall 112c issupported by the stator 120 and, because of this support, it retains itsflatness and does not warp, providing proper location for the posts 112band providing a pivot support for the blades 110.

The stator 120 does not have to be formed integrally with the housing112, and thus does not have to be insert molded into the housing 112.Instead, the stator 120 can be assembled within the housing 112 usingprecision assembly. This is shown in a second embodiment of the presentinvention, depicted in FIGS. 5A and 5B (these figures illustratedifferent covers 114c). However, although such an aperture/shuttersystem provides some of the size advantages mentioned above, theassembly of housing 112 around the stator 120 has to be done to tighttolerances and this can be difficult and expensive. Also, an additionalhousing plate with the support posts 112b (for supporting cam pivotpoints) would be required. This additional housing plate has to berelatively thick (along the optical axis) in order to provide a rigidsupport for the posts 112b and to prevent warping. Furthermore, if theaperture/shutter housing is manufactured separately and the stator 120is then assembled inside the aperture/shutter housing, the walls of theaperture/shutter housing will need to be thicker, in order to providethe required rigidity to the aperture/shutter housing 112, making theaperture/shutter housing 112 larger.

The stepper motor 113 also includes a magnetic rotor 130 (see FIG. 2).The rotor 130 is manufactured as a single, integral part made of thesame magnetic material. That is, it is not made of several parts thathave been assembled together. The motion of the magnetic rotor 130 isactivated by the magnetic fields provided by the stator 120. The rotor130 of the first embodiment is similar to that of the second embodimentand, is in a form of a ring that has an outer cylindrical surface 130aand an inner cylindrical surface 130b defining a hollow central portion130c. This hollow central portion 130c provides light access to theimaging area 115. The rotor 130 and the hollow section 130c are centeredaround the optical axis, and thus are symmetric relative to the opticalaxis. The rotor 130 is coupled directly (i.e., without any interveningparts, for example, parts made of other materials) to the shutter blades110 by a plurality of positioning features integrally formed thereon,for example, rotor posts 131. These posts 131 are slidably positionedinside the slots 110a of the shutter blades 110. Thus, there are nointermediate parts, such as a pinion gear and a ring with a sector gearfor coupling the rotor to the shutter blades, nor is there a ballbarring, such as the one disclosed in U.S. Pat. No. 4,005,448 forpositioning the rotor relative to the stator. As the rotor 130 rotates,the blades 110 will pivot about the posts 112b formed on the rear sideof the rear wall 112c of the molded housing 112. When the rotor 130rotates, the blades 110 move as a direct consequence of that rotation.Thus, there is no need for the pinion gear and the ring common to theprior art. Because the rotor 130 is an integral part, and because itcouples directly to the shutter blades 110, there is no need for acareful alignment of different parts of the rotor assembly with respectto one another and with respect to the slots 110a of the shutter blades110. That is, because there are fewer interfaces among the differentparts, there are fewer tolerances that may add together. This decreasesthe cost of the aperture/shutter system and improves it accuracy.

The rotor 130 is magnetic and is made of a moldable material that iscapable of being magnetized, for example, an isotropicneodymium-iron-boron, an isotropic samarium-cobalt,praseodymium-iron-boron, or other rear earth magnetic material. Afterthe rotor 130 is molded it is magnetized to form a plurality of magneticpoles thereon. The larger the number of poles, the more aperturesettings are feasible. An imaging system with multiple aperture settings(corresponding to multiple F-numbers) require that a motor has at lestthat number of steps plus two more steps in order to completely closethe aperture opening. Thus, if seven aperture sizes are required(corresponding to seven F-number values) of the lens system, then aminimum of nine steps are required of the motor. These steps correspondto the seven aperture settings and two steps for the home position (tocompletely close the shutter blades). However, it is preferred that thenumber of magnetic poles be 20 or more, and even more preferred that itbe at least 26 and most preferable over 30 poles. It is difficult toproduce more than 50 poles in the rotor of this size because of the highcoercivity of the material forming the rotor. However, a rotor with alarger circumference may have a larger number of poles. The closer thepoles are with respect to one another (around the outer circumference ofthe rotor) the less rotation is required of the rotor and the faster isthe shutter response to open and close control sequences. In thisembodiment the lens system has seven aperture sizes and the outercylindrical surface 130a of the magnetic rotor 130 has thirty sixequidistant magnetic poles (18 north poles and 18 south poles) facingthe stator. The north poles are sandwiched between the south poles andthe south poles are sandwiched between the north poles of the rotor. Thediameter of an inner cylindrical surface 130b of the rotor 130 is 13.58mm and diameter of the outer cylindrical surface 130a of the rotor 130is about 16.3 mm. The circumference of the outer cylindrical surface130a is 51.2 mm. It is preferred that the pole density D_(p) of therotor (defined as the ratio of the circumference of the outercylindrical surface 130a to the number of magnetic poles) be less than2. It is more preferable that the pole density be 1≦D_(p) ≦1.7. It iseven more preferable that the pole density be 1.1≦D_(p) ≦1.7. It is mostpreferable that the pole density be 1.28≦D_(p) ≦1.7. In this embodiment,the pole density D_(p) =51.2/36=1.4. That is, the centers of theadjacent magnetic poles are approximately 1.4 millimeter apart.

In this embodiment, in order to reduce the mass of the rotor, the rotor130 is positioned inside the stator 120. However, the position of therotor and the stator may be reversed--i.e., the stator may also bepositioned inside the rotor. In order to keep the motor compact it ispreferable that the rotor be as small as possible while its hollowsection 130c be as large as possible (in order to increase the F-numberof the lens system). Thus, it is preferred that the thickness of therotor be about 1.5 mm or less, and that its length (without the posts)be less than 5 mm. The small size of the rotor makes it light and easyto turn, providing a higher torque. However, if the rotor is too small,it does not generate enough magnetic field and that makes it difficultto rotate. Therefore it is preferred that (i) the rotor thickness beabout 0.5 mm to about 1.5 mm and (ii) the rotor length be 2.5 to 5 mm,and preferably 3 to 4 mm. In this embodiment the thickness of the rotor130 is about 1 mm and the length of the rotor is about 3.5 mm long. Therotor posts are molded together with the rotor and are integraltherewith. These posts are approximately 2 mm long and their diameter isabout 1 mm.

The rotor 130 is kept in proper position with the internal central hub112a, hemispherical location pads 114a and the cover 114c. Although therotor 130 rotates, the hub 112a does not. The hub surface engages theinner cylindrical surface 130b of the rotor 112 and rotably supports therotor 112. Because there is no rotational inertia associated with themovement of the hub, the motor requires less power and the torquegenerated by the motor is greater and is more uniform than the torquegenerated by the prior art motors such as the one disclosed in U.S. Pat.No. 4,005,448. The rotor 130 also includes a horizontally extending key132. The slot 114b of the molded housing 112 is used to engage the keytab 132 of the rotor 130 to constrain its range of rotation fromaperture closed position to full open position. Features molded into theaperture/shutter housing 112 include the internal central hub 112a whichsupports the rotor 130 and which determines the position of the insidediameter of the rotor 130, and a slot 114b which holds a key tab 132(from the rotor 130) inserted into it. This slot 114b limits the travelof the rotor in both directions. The total amount of rotation for therotor 130 of this embodiment is ±25 degrees. The full rotation of therotor 130 is performed in ten 5 degree steps.

The hub 112a of the aperture/shutter housing 112 determines the positionof the rotor 130, and if the position of the stator 120 deviates toomuch from the specified position (due to build up of manufacturing andassembly tolerances), the rotor 130 may contact the stator 120, causingthe motor 113 to stall. Thus, in order to improve the accuracy of thefeatures in the aperture/shutter housing 112 that position the rotor 130with respect to the stator 120, it is preferred to integrally form theaperture/shutter housing 112 and a stator 120 rather than to assemblethem together. This can be accomplished, for example, by insert moldingthe aperture/shutter housing 112 around the two stator assemblies 120a,120b as described in the first embodiment. This eliminates thepositional variation exhibited by the prior art aperture/shutterassemblies due to assembly of separate parts of the aperture/shutterhousing 112 and the rotor 130 and stator 120 with respect to oneanother. Because insert molding the stator 120 inside theaperture/shutter housing 112 (as it was done in the first embodiment)allows additional precision in positioning of the rotor 130 with respectto the stator 120, this in turn allows the gap d₃ (FIG. 2) between thestator 120 and the rotor 130 to be reduced. This gap d₃ is formed asfollows. The outer cylindrical surface 130a of the rotor 130 is of asmaller diameter than the inside surface 125a of the inner cylindricalwall 125 of the stator 120. The inner cylindrical surface 130b of therotor 130 sits on the cylindrical hub 112a of the aperture/shutterhousing 112. Therefore, an annular gap d₃ is formed between the insidesurface 125a of the inner cylindrical wall 125 of the stator 120 and theouter cylindrical surface 130a of the rotor 130. The size of the gap d₃is one of the primary factors in determining the available torque of themotor. Therefore, as the gap d₃ between the stator 120 and the rotor 130is reduced, the torque is increased and this results in fasteracceleration of assembly and therefore faster shutter time. Thereduction in gap distance also results in less need for power to drivethe motor (i.e., lower voltage or less current) in order to achieve thesame performance (rotational speed of the rotor).

The aperture stop/shutter shown in FIGS. 2 and 5A includes at leastthree shutter blades 110, which also function as the aperture settingblades. It is noted that either a larger or a smaller number of shutterblades may also be used. As discussed above, each of the shutter blades110 includes a cam slot 110a for engaging a corresponding feature, suchas posts 131 situated on the rotor 130. The shape of these cam slots110a determines the size of the apertures. The shutter blades 110 alsoinclude a plurality of holes 110b for engaging the posts 112b located onthe rear wall 112c of the aperture/shutter housing 112 (FIG. 3), or forengaging posts 112B of a rear plate 112c' (FIG. 5A). In the firstembodiment, the posts 112b are molded with the aperture/shutter housing112 and are integral with the aperture/shutter housing. The positioningprecision of these posts 112b are an important factor that effects theaccuracy of the aperture opening. Since posts 112b are formed integrallywith the aperture/shutter housing, their position is always accurate.Thus, molding the posts 112b with the rest of the aperture/shutterhousing increases the accuracy of the aperture/shutter system 100 andeliminates the expense of complex alignment during assembly.

Two separators 140a and 140b provide a smooth surface for the shutterblades 110 to slide on. An upper separator (140a) is used to hold theshutter blades 110 in a plane and to reduce the oscillating movement ofthe shutter blades 110 and the rotor 130 when motor 113 is stopped atthe desired aperture. The lower separator 140b is used for setting themaximum aperture opening and has a smaller central hole 140b' than thehole 140a' of the housing or of upper separator 140a. The cover 114c isused to hold the rotor 130, shutter blades 110, lower separator 140a,and upper separator 140b in place. This cover 114c attaches to thehousing 112 with screws, heat stake posts 112d or a snap (not shown)(See FIGS. 6, 7, and 8.) The cover 114c includes a plurality offeatures, for example, holes 114d (see, for example, FIGS. 2, 5A, 5B)that engage complimentary features, such as heat stake posts 112d formedon the rear wall 112c of the housing 112. The cover 114c also functionsas a lens mount and, therefore, may include at least one integrallymolded lens seat 114c'. This is shown in FIG. 5B. As mentioned earlier,the stepper motor 113 comprises a doughnut like housing 112 encasing twostator assemblies 120a, 120b and a rotor 130, at least partially encasedin the housing 112. The molded aperture/shutter housing 112 alsoincludes the heat stake posts 112d or holes 112d' (see FIG. 4) for thescrews in order to allow attachment of the cover 114c to the housing112. This configuration also results in an aperture/shutter system withan annular shape of a smaller size and a greater aperture opening (whichis especially suitable for zoom lens systems) and in fewer parts toassemble, thereby reducing the cost of the aperture/shutter assembly.

The fourth embodiment of the aperture/shutter system of the presentinvention is similar to the first embodiment, but the housing 112 alsoserves as a lens barrel. This embodiment is shown in FIGS. 8, 9 and 10.More specifically, the shutter/aperture system 100 can also include oneor more lens mounts 150 with lens seats 151 for holding one or more lenselements. The lens mounts, including the lens seats 151, are formedintegrally with the housing 112 and the stator 120 for example, byplastic molding or casting. Thus, according to this embodiment, theaperture/shutter system 100 incorporates the integral housing 112, therotor 130, the shutter components and an integrally formed, for exampleby plastic molding, lens seat 151 and the stator 120. More specifically,the metal stator 120 is assembled first and the aperture/shutter housing112 with lens seats is molded around the stator 120. With reference toFIG. 9, the lens mounts 150 may include a lens element locating andretaining feature, such as the ring 152 and a lens seat 151 for one ormore lens elements. In addition, the housing 112 may also include anintegral axially extended ring 153 that can be heated and pressedagainst a lens element situated adjacent to it, forming a heat seal andretaining the lens element(s) in place. A separate retaining ring may beused instead of using the ring 153 to keep the lens element in place.

The embodiment of the aperture/shutter housing 112 with the lens mounts150 may also have features that could mate to a lens barrel. Forexample, FIGS. 9 and 10 show that the housing 112 has a helicticalthread 155 formed on its external surface. The helictical thread 155interacts with a complimentary thread of a lens barrel or a sleeve,allowing the housing 112 to be assembled inside the lens barrel orinside the sleeve. Furthermore, another, smaller lens barrel may beslidably positioned inside the housing 112. This smaller lens barrelengages a rib 157 of the housing 112, so that the smaller barrel canslide along the rib 157 without rotating relative to the housing 112.Other features for engaging lens barrels or other mechanisms may be alsomolded on the housing 112.

FIG. 1 illustrates a zoom lens assembly of the fifth embodiment of thepresent invention. This zoom lens assembly comprises an aperture/shutterassembly (with or without lens elements situated in its hollow portion)and at least one lens barrel mated to the aperture/shutter assembly. Azoom lens assembly includes a plurality of lens groups, at least one ofwhich is movable in order to provide a zoom lens system with the desiredzoom ratio.

More specifically, FIG. 11 shows a smaller lens barrel 160 withpositioning features 161 for engaging a plurality of ribs 157 of anaperture/shutter system 100. These ribs 157 prevent the rotation of thesmaller lens barrel 160 within the aperture shutter housing 112. Thislens barrel 160 fits within the aperture shutter housing 112. Theaperture/shutter system 100 is similar to that of the third embodiment.It includes an integral housing 112, with a stator 120 and lens mountswhich include lens seats 151 for holding two lens elements 170. FIG. 11also shows a rotor 130, and a plurality of shutter blades 110 sandwichedbetween two separators 140a and 140b. The whole assembly fits inside thehousing 112 and is enclosed inside the housing 112 by a rear cover 114c.The small lens barrel 160 provides support for lens elements 171, 172and is slidably fitted inside the housing 112. In addition, a rear lensbarrel 173 supports a lens element 174 and also fits inside the housing112.

The following are some of the advantages of the aperture/shutter systemof the present invention:

The aperture/shutter system of the present has a small size, largecentral opening and fewer parts to assemble, thereby reducing the costof the aperture/shutter system.

Zoom lens systems require many different aperture settings, because aszoom lens system changes its focal length (from wide to telephoto, forexample) the aperture size changes. The larger the zoom ratio, thegreater is the number of different aperture settings required. Thus,this invention is especially suitable to zoom lens systems and is evenmore suitable to zoom lens systems with large zoom ratio (2× or higher)because it offers multiple aperture settings in a very small packagewith minimum number of parts.

It is also an advantage of the aperture/shutter system this inventionthat it is (i) compact and (ii) provides a large aperture opening, thusenabling a lens system to have a faster F-number. This results ingreater flash distance, higher image quality, greater light gatheringcapability and, if used in a zoom lens system, a longer focal length intelephoto mode.

The term "aperture/shutter system" defines a device that can be operatedeither as (i) a light controlling aperture only (in which case a cameramay or may not require an additional shutter activated by an additionalmotor or other means; or (ii) a shutter having only an open and closedposition; or (iii) a combination aperture shutter system that operatesboth as a light controlling aperture and a shutter.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

100 aperture/shutter system

110 blades

110a slot

110b hole

112 aperture/shutter housing

112a internal central hub

112b post

112c rear wall

112d stake posts

112d' holes

113 stepper motor

114 inner wall

114a hemispherical location pads

114b slot

114c rear cover

114d holes

115 imaging area

116 film

120 stator

120a, 120b stator assemblies

121 coil

122, 123 metal parts of the stator assembly

124 interleaved teeth

125 cylindrical wall

125a inside surface

130 rotor

130a outer cylindrical surface

130b inner cylindrical surface

130c hollow central portion

131 post

132 keytab

140a upper separator

140a' upper separator central hole

140b lower separator

140b' lower separator central hole

150 lens mount

151 lens seat

152 ring

153 extended ring

155 helictical thread

157 rib

160 small lens barrel

171, 172 lens elements

173 rear lens cell

174 rear lens element

What is claimed is:
 1. An aperture/shutter system defining an opticalpath, said aperture/shut system comprising:a shutter mechanism operableat a first state to selectively block light along said optical path anda second state to allow light along said optical path; and a motorincluding a stator and an annular rotor, said rotor being rotablysupported within said stator by a support that is (i) stationary withrespect to said stator and (ii) engages an inner surface of said rotor,said rotor being coupled to said shutter mechanism to move said shuttermechanism between said first state and said second state.
 2. Anaperture/shutter system according to claim 1, wherein said rotor has acentral opening therethrough which is aligned with said optical pathsuch that light passes through said central opening and through saidshutter mechanism at least when said shutter mechanism is in said secondstate.
 3. An aperture/shutter system according to claim 1, wherein saidmotor has a housing integral with said stator and said housing providessaid support for said rotor.
 4. An aperture/shutter system according toclaim 3, wherein said rotor has a central opening there through which isaligned with said optical path such that light passes through saidcentral opening and through said shutter mechanism at least when saidshutter mechanism is in said second state.
 5. An aperture/shutter systemaccording to claim 4, wherein said housing has at least one lens seatsupporting at least one lens element in said optical path.
 6. Anaperture/shutter system according to claim 4, further comprising acover, said cover including at least one lens seat.
 7. Anaperture/shutter system comprising:a shutter blade; and a motorincluding (i) a housing; (ii) a stator, and (iii) an annular rotor beingaxially aligned with said stator along an optical axis, wherein saidhousing is molded around said stator and is integral with said stator,and said housing includes a hub supporting said rotor, said stator incombination with said rotor causing rotation of said blade.
 8. Anaperture/shutter system according to claim 7, whereinsaid rotor (i) isat least partially located inside said stator; (ii) has an innercylindrical surface defining a central opening symmetric about saidoptical axis; and said hub is located within said central opening andengages said inner cylindrical surface.
 9. A motor comprising:a statorand an annular rotor, said rotor being rotably supported within saidstator by a support that is (i) stationary with respect to said statorand (ii) engages an inner surface of said rotor.
 10. A motorcomprising:a stator and an annular rotor arranged inside said stator,said rotor (i) having an outer surface facing said stator and an innersurface and, (ii) is being rotably supported within said stator by asupport that is stationary with respect to said stator and that engagessaid inner surface of said rotor.
 11. A motor according to claim 10,wherein said outer and said inner surfaces of said rotor and saidsupport are cylindrical.
 12. A motor according to claim 11, furthercomprising a housing encasing said stator, wherein said housing includesa hub providing said support.
 13. An annular stepper motor comprising:astator; a motor housing molded around said stator and being integraltherewith, said housing having a central hub; and a magnetic rotorhaving an inner surface that is rotably supported by said hub.
 14. Amotor according to claim 13, wherein said housing has at least one lensseat formed therein.
 15. A motor according to claim 13, wherein saidhousing has plastic walls with thickness of 0.4-0.9 mm.
 16. A motoraccording to claim 13, wherein said housing includes integral featurescapable of engaging a lens barrel.
 17. A motor according to claim 16,wherein said integral features are helicoidal threads.
 18. A motoraccording to claim 17, wherein said threads are helicoidal and arelocated on an external surface of said housing.
 19. A motor according toclaim 17, wherein said threads are helicoidal and are located on insidesurface of said housing.
 20. An aperture shutter system defining anoptical path, said aperture/shutter system comprising:a shuttermechanism operable at a first state to selectively block light alongsaid optical path and a second state to allow light along said opticalpath; and an annular stepper motor including (i) a stator, (ii) a motorhousing molded around said stator and being integral therewith, saidhousing having a central hub, and (iii) a magnetic rotor having an innersurface that is rotably supported by said hub; said rotor being coupledto said shutter mechanism to move said shutter mechanism between saidfirst state and said second state.
 21. An imaging systemcomprising:plurality of lens elements defining an optical axis; ashutter mechanism including a plurality of shutter blades; and a motorincluding a stator and an annular magnetic rotor arranged inside saidstator, said rotor being rotably supported within such stator by asupport that engages an inner surface of said rotor and is stationarywith respect to said stator, said rotor being axially aligned with saidstator along said optical axis, said stator in combination with saidrotor causing rotation of said blades.
 22. An imaging system accordingto claim 21, wherein said motor comprises a housing molded around atleast a part of said stator and said housing provides said support forsaid rotor.
 23. An imaging system according to claim 21, wherein saidmotor further comprises a cover, said cover including at least one lensseat supporting at least one of said plurality of lens elements.
 24. Animaging system according to claim 22, wherein said cover is connected tosaid housing.
 25. An imaging system according to claim 21, wherein saidplurality of lens elements comprise at least two moving groups which, incombination, provide at least 2× zoom ratio; and said motor is anannular motor defined by an outside diameter d₁ and an inner diameter d₂such that 2.5<d₁ /d₂ <3.4.
 26. An imaging system according to claim 25,wherein said housing has plastic walls with thickness of 0.4 mm to 0.9mm.
 27. An imaging system according to claim 21, wherein said housinghas plastic walls with thickness of 0.4 mm to 0.9 mm.
 28. An imagingsystem according to claim 21, wherein(i) said plurality of lens elementscomprise at least two moving groups and, in combination provide at least2× zoom ratio, (ii) at least one of said lens groups is enclosed in alens barrel with at least one positioning feature and said housingcomprises at least one complimentary feature for engaging saidpositioning feature of said lens barrel.
 29. An imaging system accordingto claim 28, wherein said motor has housing molded around at least apart of said stator and said housing supports at least one of saidplurality of lens elements.
 30. An imaging system according to claim 28,wherein said complimentary feature is internal to said housing and saidlens barrel at least partially fits inside said housing.
 31. An imagingsystem according to claim 29, wherein said complimentary feature is arib.
 32. An imaging system according to claim 21, wherein said shuttermechanism is operable at a first state to selectively block light alongan optical path centered on said optical axis and a second state toallow light along said optical path; andsaid rotor being directlycoupled to said shutter mechanism to move said shutter mechanism betweensaid first state and said second state.